Expatriate fish could return a hero

The cure for the exotic whirling disease, a fatal malady in trout, could - ironically - lie in a foreign fish. Researchers recently found that Hofer rainbow trout, the offspring of Pacific rainbow trout taken to Germany in 1880, are 10 to 100 times less susceptible to whirling disease than native U.S. rainbow trout, thanks to a lengthy exposure to and co-evolution with the parasite in Europe. The finding could be a major breakthrough. Since whirling disease first infected American trout in 1957, it has devastated the Rocky Mountains' $2 billion fishing industry (HCN, 9/18/95: The West's fisheries spin out of control).

"It provides us with hope," says Ronald Hendrick, an epidemiologist at the University of California at Davis. "The Hofer rainbow trout offer us a valuable insight into the mechanisms of resistance, with very encouraging results." Hendrick hopes to use the Hofer to create a genetically resistant hybrid trout.

Fish and wildlife managers, however, have concerns about introducing imported Hofer trout into American waters. "We don't know if they are capable of surviving as wild fish," says Colorado Division of Wildlife senior fish pathologist Peter Walker. He's also concerned that Hofer trout could displace native fish, and introduce foreign diseases.

Before states can import the fish, though, the U.S. Fish and Wildlife Service has to grant its approval * and that could take years.